The present invention relates to an arrangement which includes a roller nut in conjunction with a smooth shaft and is operative for transforming a rotary movement of the shaft into a thrust movement of the roller nut.
Roller nuts of the type under consideration are known in the art. These roller nuts include a plurality of roller rings or cages which surround the shaft at different angles to each other. The inner surfaces of the roller cages are in pressure contact with the outer surface portions of the shaft. One of such roller nuts is disclosed in Applicant's U.S. Pat. No. 4,253,342. Rolling or contact surfaces on the shaft and the roller rings or cages and the inclination of the roller rings relative to each other are so selected that the rolling tracks of the roller rings describe on the shaft a uniform helical line. The roller rings are accommodated in a two-part housing which is provided with corresponding grooves receiving the roller rings and with an elastic element which serves for generating pressure forces or friction contact between the rings and the shaft. These roller nuts have a high accuracy, but in many instances they are too expensive and too special. For example, with the above-described construction, it is impossible to readjust the screw transmission from the left hand direction to the right hand direction and to a different angle of inclination. It is also disadvantageous that the housing is comprised of two parts which must be repeatedly readjusted and screwed to each other.